1. Field of the Invention
Aspects of the present invention relate to an organic light emitting diode and a method of manufacturing the same, and in particular, to an organic light emitting diode including an improved emission layer and a method of manufacturing the same.
2. Description of the Related Art
Organic light emitting devices display an image toward, in addition to a bottom surface thereof, a top surface thereof. For top-emission type organic light emitting devices, pixel circuits connected to pixels are disposed in the opposite direction to a direction in which an image is displayed and thus, a degree of freedom in a pixel circuit design is high. Thus, research into top-emission type organic light emitting devices is being actively performed in various aspects.
However, top-emission type organic light emitting devices use an optical resonance structure between a reflective anode and a semi-transmissible cathode to increase light extraction efficiency. Due to the use of the optical resonance structure, an optimal thickness of an organic film between an anode and a cathode is dependent upon an emission wavelength. Thus, pixels have different thicknesses due to the organic film thickness that is dependent upon emission color, and the stacking structure of organic films becomes complex. For example, since a blue pixel has a shorter wavelength of light emission spectrum than a red or green pixel, the thickness of the organic film in the blue pixel is smallest and then, the green pixel and then, the red pixel. That is, the red pixel includes the thickest organic film, whereas the green pixel has a thickness between that of the red and blue pixels.
Conventionally, in pixels of various colors, for red and green pixels, an auxiliary layer is further added to the organic film to adjust the thickness according to an emission wavelength. That is, one more operation is further required than when the blue pixel is manufactured. Thus, the operating time is increased and a chamber arrangement becomes complex.
To solve this problem, instead of the auxiliary layer, the thickness of other functional layers can be increased. Examples of such common functional layers include a hole injection transport layer or an electron injection transport layer. However, when the thickness of these common functional layers is changed, characteristics of other colors may be changed.
Instead of these methods, the thickness of an emission layer can be increased by a size corresponding to the thickness of the auxiliary layer. However, when the thickness of the emission layer is increased, the distance between an emission region and a reflective film of an anode is reduced. Thus, an original spectrum may not be obtained and color coordinates are distorted. In addition, where there is the increase in emission layer thickness, the light emitted outside a device may have different spectrum regions and luminescent efficiency may also be reduced.